This invention relates to transcutaneous gas sensor probes used for the measurement of transcutaneous gases emitted through the skin of a living body. More specifically, the invention concerns a fixation ring upon which a membrane permeable to the gas to be measured but impermeable to an ion solution can be premounted and packaged under clean conditions to be later connected to the active portion of a transcutaneous gas sensor probe without need for special handling, instruments or skill.
It is known in the medical art of non-invasive blood gas content monitoring and measurement to apply to the surface of the skin of a person whose blood gas content is to be monitored and measured, a probe having a barrier permeable to the gas to be measured or monitored and impermeable to other gases as well as to an ion solution in which the gas which is to be monitored and measured is soluble. Such probes generally include a first electrode or anode, a second electrode or cathode, an ion solution in contact with the anode and cathode and a membrane spanning a region between the anode and cathode and maintaining a supply of the ion solution in contact with the anode and cathode. A particular gas which is emitted from the skin of a living body is permitted to permeate through the membrane and into the ion solution where it has an effect on the flow of current between the cathode and anode for permitting an electrical measurement indicative of the quantity of the gas emitted from the skin.
In the use of conventional transcutaneous gas probes, membranes are attached to the probes by the physician or technician applying each probe before its application. This requires difficult handling by highly skilled personnel who must use special tools to install the membranes with a fastener, such as an O-ring. Such preparation is required with each use of the probe. The membranes are small, light, susceptible to damage from improper handling, and generally difficult to install in a transcutaneous gas probe. Once installed, the membranes are likely to shift relative to the electrodes, thereby resulting in displacement of the electrolyte and upsetting the calibration, sensitivity and stability of the probe. Also, the difficulty in changing the membranes on prior art probes encourages the repeated use of membranes which should be changed after each use thereby creating unsanitary conditions.
It is known in the prior art to employ a separate attachment ring with a transcutaneous gas sensor probe which attachment ring can be attached to the skin of a patient and which is adapted to receive the active part of the probe. Such attachment rings are beneficial in that they obviate the need to sterilize the probe between patient uses. Since only the attachment ring is brought into contact with the skin of the patient, only it need be sterilized between uses. Such attachment rings can also be provided with adhesive coatings on their surfaces adapted to engage the skin of the body for securing a transcutaneous gas sensor probe in place on the surface of the skin. A transcutaneous gas sensor probe having a removable attachment ring with an adhesive coating is disclosed in German Pat. No. 27 24 461, issued to Radiometer A/S of Copenhagan, Denmark, for a sensor for transcutaneous electrochemical measurements. Although the probe disclosed in the German patent obviates the need for sterilizing the entire probe with each use and provides a positive method of affixing the probe to the skin surface of a patient, it does not solve the above described problem of attaching the membrane to the probe without the performance of a relatively difficult operation. Moreover, prior art probes do not provide for a sufficiently positive engagement of the membrane by the sensor to prevent substantial movement between the membrane and electrodes which can degrade measurement readings and necessitate recalibration of the probe.